Method and system for manufacturing cumene hydroperoxide

ABSTRACT

A method for manufacturing cumene hydroperoxide comprises reacting cumene and oxygen in the presence of a water phase comprising aqueous ammonia, and in the absence of an additive comprising an alkali or alkaline earth metal, to form cumene hydroperoxide. A system for producing cumene hydroperoxide comprises a cumene feed in fluid communication with a reactor having a cumene hydroperoxide oxidate outlet; an oxygen feed in fluid communication with the reactor; and an ammonia feed in fluid communication with the cumene feed and/or the reactor, wherein the cumene feed, the oxygen feed, the ammonia feed, and the reactor are free of an additive comprising an alkali or alkaline earth metal.

This is a divisional of co-pending pending prior application Ser. No.09/916,775 filed on Jul. 27, 2001, now U.S. Pat. No. 6,465,695,incorporated herein by reference.

BACKGROUND OF THE INVENTION

This disclosure relates to methods for cumene oxidation, and inparticular to methods and systems for manufacturing cumenehydroperoxide.

Free radical cumene oxidation reactions are well known. They can beconducted in the presence of a water phase, the so-called “heterogeneouswet oxidation” method, or in the absence of a water phase, the “dryoxidation” method. The heterogeneous wet oxidation method is generallypreferred, as the presence of water provides improved safety and controlof the exothermic reaction, and also requires less capital investment.

Commercially, wet cumene oxidation is conducted by a continuous processusing a cascade of at least two gas-sparged reactors, typically three tosix, with a variable temperature profile. The main oxidation reactionproducts are cumene hydroperoxide (CHP, the desired product, which isoften used to produce phenol and acetone), along with dimethylbenzylalcohol and acetophenone. In addition, trace amounts of acidicbyproducts, such as formic acid, acetic acid, and phenol, are alsoproduced. These acidic byproducts may inhibit the oxidation reaction,resulting in a decrease in both rate and yield, as well as negativelyaffecting CHP selectivity. To prevent this, U.S. Pat. Nos. 3,187,055;3,523,977; 3,687,055; and 3,907,901 variously teach that alkali metalbases, such as sodium hydroxide (NaOH), and bicarbonate salts of alkalimetals, such as sodium carbonate (Na₂CO₃), can be used as additives toremove the trace acid impurities. The use of a dibasic salt such assodium carbonate is known to be additionally effective due to itsability to buffer the pH of the mixture and prevent large pH variations.Strongly basic NaOH is generally not preferred due to its tendency toform a water-soluble salt with the product CHP, resulting in loss of theCHP-salt into the oxidate aqueous purge streams, thereby decreasingyields.

The alkali additives are usually added to the reactors as aqueoussolutions, whereupon two immiscible phases form. The strong bubblingaction from an air stream provides contact and mixing of the twomutually insoluble phases into a partially emulsified mixture. Intimatemixing of the two immiscible phases is critical to obtaining efficientneutralization of the organic acids present in the cumene-CHP organicphase, and special static mixers, as disclosed in U.S. Pat. No.3,933,921, and counter-current extractors, as disclosed in U.S. Pat. No.5,120,902, have been employed in the art to aid in their contacting.However, even with these devices the neutralization process is onlypartially effective because the effectiveness and degree of organic acidneutralization is highly dependent on physical mass transfer limitationsbetween the two contacting, immiscible phases. As a result, the pH ofthe oxidate reaction mixture may not be well controlled, which resultsin reduced oxidation reaction selectivity and an increased potential forequipment corrosion.

In U.S. Pat. Nos. 5,767,322 and 5,908,962, an alternative cumene wetoxidation process is described wherein Na₂CO₃ and ammonia (NH₃) aresimultaneously added to the reactors to form a mixed alkaline salt,NH₄NaCO₃. Free ammonia is not present since ammonia reacts immediatelywith the by-product NaHCO₃. This mixed alkaline salt, although not trulysoluble in the organic oxidate phase, appears to provide improved masstransfer between the two immiscible phases and more effectivelyneutralizes the undesirable organic acids than Na₂CO₃ alone. However, inorder to be effective the process disclosed in U.S. Pat. No. 5,908,962must split the cascade of oxidation reactors into two parallel trains,and must employ a special water stream flow that is counter-current tothe cumene feed stream. In practice it has been found that the Na₂CO₃,which is a strong base, must be added in very precisely controlledamounts in order to prevent the pH from varying widely, i.e., over 3 to4 pH units. In addition this process requires the purchase of twoalkaline agents and the installation of a complex piping arrangement tomanage the myriad of recycle streams. Thus this complicated cumeneoxidation system design requires high investment in equipment, labor,and costs.

In addition, in all of the above-mentioned wet oxidation processes,small amounts of the inorganic alkali or alkaline earth metal saltsremain entrained within the product CHP-cumene oxidate organic stream,and these salts pass forward into the downstream process steps wherethey deposit on and foul various pieces of equipment. This problem isparticularly troublesome downstream where the distillation column heatexchangers and reboilers foul with regularity while concentrating CHP.This salt fouling reduces heat transfer ability, increases steamconsumption, and makes the separations ineffective. Periodic cleaning ofthese fouled heat exchangers is required, which mandates plant shut downand thus lost production. Such production losses are quite costly interms of time, labor, associated monetary expenditures, and need to beavoided if at all possible. Installation of coalescer units after cumeneoxidation and prior to concentrating the CHP, to filter out and removethe entrained inorganic salts, is disclosed in U.S. Pat. No. 5,512,175.Although this method can be effective, the coalescer units are verylarge and their purchase and installation requires a high investmentcost. The special carbon-fiber coalescer filter elements used insidethese units must be replaced on an annual basis, which is also quitecostly.

Accordingly there remains a need in the art for a cost effective methodand system for manufacturing cumene hydroperoxide that overcomes thedrawbacks and disadvantages of the above-identified methods.

BRIEF SUMMARY OF THE INVENTION

The above-mentioned drawbacks and disadvantages are overcome oralleviated by a method and system for manufacturing cumenehydroperoxide, comprising reacting cumene and oxygen in the presence ofammonia or aqueous ammonia, and in the absence of an additive comprisingan alkali or alkaline earth metal, to form cumene hydroperoxide.

The system comprises means for producing cumene hydroperoxide fromcumene and oxygen in the presence of aqueous ammonia, and in the absenceof an additive comprising an alkali or alkaline earth metal.

Another embodiment of a system for cumene oxidation, equally applicablefor either the wet or dry mode of operation, comprises a cumene feed influid communication with a reactor having a cumene hydroperoxide oxidateoutlet; an oxygen feed in fluid communication with the reactor; and anammonia feed in fluid communication with the cumene feed and/or thereactor, wherein the cumene feed, the oxygen feed, the ammonia feed, andthe reactor are free of an additive comprising an alkali or alkalineearth metal. A distillation apparatus may be serially connected with thecumene hydroperoxide oxidate outlet.

BRIEF DESCRIPTION OF THE DRAWING

Referring now to the Figures, which are merely illustrative, wherein thelike elements are numbered alike:

FIG. 1 is a schematic flow diagram illustrating an exemplary embodimentof a method and system for manufacturing cumene hydroperoxide usingammonia; and

FIG. 2 is a schematic flow diagram illustrating a prior art embodimentof a method and system for manufacturing cumene hydroperoxide usingalkali and alkaline earth metal salts or bases.

DETAILED DESCRIPTION OF THE INVENTION

The inventors hereof have discovered that ammonia, even in the absenceof alkali and alkaline earth metal salts or bases, is a very effectiveneutralizing agent for cumene oxidation. This result is particularlysurprising because one of ordinary skill in the art would not expectthat ammonia, which is weaker base and not dibasic (and therefore haslittle or no buffering ability) nonetheless leads to results superior tothe stronger, dibasic additives of the prior art. Accordingly, thedrawbacks of using the prior art alkali and alkaline earth metal saltsor bases, such as sodium carbonate, sodium hydroxide, calcium carbonate,and the like are avoided or prevented by substituting ammonia alone.

An efficient method and system for commercial production of cumenehydroperoxide comprises reaction of cumene with oxygen in the presenceof ammonia, but in the absence of additives which must be subsequentlypurified, or which contribute to the fouling of equipment, in particularadditives comprising alkali or alkaline earth metals. “Alkali oralkaline earth metals” means compounds from Group IA or IIA of theperiodic table, and additives comprising these metals includes thecorresponding hydroxides, hydrates, or salts, e.g., carbonates,phosphates, and the like.

In practice, either the wet or dry cumene oxidation method may be usedto advantage with this invention. The wet method is preferred, andaccordingly comprises reaction of cumene with oxygen in the presence ofan aqueous phase. The ammonia may be introduced separately into a cumenefeed, an aqueous feed, or with an oxygen feed. Likewise, any of thevarious oxidate recycle streams in the system containing undesirableorganic acids can be beneficially treated with ammonia external to themain oxidation reactors and prior to their re-introduction into thereactors. Preferably, an aqueous ammonia solution, i.e., ammoniumhydroxide (NH₄OH) is used.

FIG. 1 illustrates a flow chart showing in detail one embodiment of themethod and system for manufacturing cumene hydroperoxide. A cumene feed10, which may be for example pure cumene, is optionally mixed with aportion of a recycled cumene oxidate stream 12, and enters a settlervessel 14 having a purge compartment 16 and a mixing compartment 18. Anammonia feed stream 20, preferably a dilute aqueous ammonia solution, isoptionally mixed with a recycled ammonia stream 22, and is also fed tosettler vessel 14, and mixed with the cumene feed. The amount of ammoniaentering settler vessel 14 may be controlled using a flow control device24, e.g., a valve, that is actuated either manually or by an operatorvia an electronic interface (not shown), and may be optionally monitoredusing a sensor such as a pressure sensor, an output sensor, a flow ratesensor, a mass flow sensor, or the like. The settler vessel 14 can becharged with an amount of aqueous ammonia effective to maintain the pHof oxidate mixture(s) as described below at greater than or equal toabout 5, preferably greater than or equal to about 7; and at a pH lessthan or equal to about 10, and preferably less than or equal to about 8.

Where aqueous ammonia is used, the mixture may be allowed to settle,forming two distinct phases, a bottom aqueous ammonia phase 26 and a topcumene organic phase 28. The aqueous phase contains the aqueous ammoniasolution, and may contain neutralized acid inhibitors from the optionalrecycled ammonia stream 22, while the organic phase includes the cumene,and may contain organic reaction by-products and other organiccomponents from the optional recycle cumene stream 14.

Aqueous ammonia phase 26 is then fed into reactor 30 (preferably intothe top as shown). Aqueous ammonia phase 26 may also be split and fedinto sequential reactors 32, 34, 36, 38, and 40. Cumene organic phase 28is fed into reactor 30 (preferably from the bottom as shown). Suitablereactors are known in the art, and the system preferably comprise threeor more reactors, most preferably 3 to 6 reactors, serially disposed influid communication with reactor 30. More particularly, the cumeneoxidation reaction is carried out in a continuous fashion using acascade of air-sparged reactors 30, 32, 34, 36, 38, and 40.

Inside each reactor 30, 32, 34, 36, 38, 40 an incoming oxygen feed 42mixes, preferably turbulently mixes, the two phase streams 26, 28together. Oxygen feed 42, preferably an air stream containing about 15to about 25 volume percent (vol. %) oxygen, preferably about 18 to about22 vol. % oxygen, most preferably 21 vol. % oxygen, is introduced or fedinto the bottom portion of each reactor 30, 32, 34, 36, 38 and 40. Theoxygen reacts with the cumene to form cumene hydroperoxide and reactionbyproducts (“the cumene oxidate”).

Each reactor 30, 32, 34, 36, 38, 40 can be maintained at a lowertemperature of about 160 degrees Fahrenheit (° F.), preferably 170° F.,most preferably 180° F., to an upper temperature of about 240° F.,preferably about 230° F., most preferably 220° F., or a temperaturerange of about 180° F. to about 220° F., and at a lower pressure ofabout 50 pounds per square inch gauge (psig), preferably 60 psig, mostpreferably 70 psig, to an upper pressure of about 80 psig, preferablyabout 90 psig, most preferably 100 psig, or a pressure range of about 70psig to about 100 psig. The pH is monitored and controlled for eachreactor 30, 32, 34, 36, 38 and 40, and may be used to determine theamount of ammonia introduced by feeds 20 and/or 22. The pH of thereaction mixture within each reactor is preferably maintained betweenabout 5 to about 10, preferably between about 6 to about 9, and mostpreferably between about 7 to about 8.

As oxygen feed 42 rises within each reactor 30, 32, 34, 36, 38, 40, thevolume percent oxygen decreases and becomes depleted such that a spentoxygen feed 44 typically containing about 2 to about 10 vol. % oxygen,preferably about 3 to about 8 vol. % oxygen, most preferably about 4 toabout 6 vol. % oxygen, is emitted from the top of each reactor 30, 32,34, 36, 38, 40. Where an aqueous phase is present, the higher densityaqueous phase falls to the bottom of the reactors and may be drawn offcontinuously as a recycled aqueous ammonia stream 22.

At least a portion of the cumene oxidate 62, preferably the entirety ofthe oxidate 62, is removed and fed into a base portion of eachsequential reactor 32, 34, 36, 38 and 40. As the organic phase stream 28passes through reactors 30, 32, 34, 36, 38, 40 serially disposed influid communication, the concentration of cumene hydroperoxide generallyincreases. The cumene hydroperoxide make profile (i.e., cumenehydroperoxide concentration) in the cascade of reactors 30, 32, 34, 36,38, 40 can vary. For example, reactor 30 can have about 5 to about 6weight percent (wt. %) cumene hydroperoxide, while reactor 40 can haveabout 20 to about 30 wt. % cumene hydroperoxide, or more.

After reaction in final reactor 40, an oxidate product stream 46,typically comprising about 20 to about 30 wt. % cumene hydroperoxide,may be fed into a discharge vessel 48, e.g., a storage tank, so that anyremaining aqueous phase may settle and be drawn off as discharge 50. Thedischarge vessel 48 is preferably serially disposed in fluidcommunication with and after the last reactor. The separated oxidateproduct stream 76 is then introduced or fed forward, i.e., downstream,from discharge vessel 48 for further purification, for example bydistillation.

The distillation apparatus is serially disposed in fluid communicationwith and after the storage discharge 48. The distillation apparatus caninclude but is not limited to standard distillation equipment known inthe art as well as one or more distillation components selected from thegroup consisting of a vacuum distillation apparatus, a distillationcolumn heat exchanger, a reboiler, a shell-and-tube heat exchangervaporizer, and combinations comprising at least one of the foregoingdistillation components. Separated oxidate product stream 76 ispreferably subjected to a series of vacuum distillations, e.g., 1 to 3distillation stages to remove cumene and other by-products, whereinseparated oxidate product stream 76 is concentrated to about 80 to about83 wt. % cumene hydroperoxide.

For purposes of illustration, and not to be interpreted as limiting,FIG. 1 illustrates only one distillation step. The product stream 46 maybe concentrated using distillation components such as first and secondvaporizing apparatus 52, 54, e.g., a shell-and-tube heat exchangervaporizer and a primary reboiler, respectively, which employ lowpressure steam as a heating medium. The first vaporizing apparatus 52 isserially disposed in fluid communication with and after the storagedischarge 48. Steam flow demand to the second vaporizing apparatus 54and the apparatus temperature can be controlled by a flow control device56, e.g., a valve actuated either manually or by an operator via anelectronic interface (not shown), and optionally a sensor selected fromthe group consisting of a pressure sensor, an output sensor, a flow ratesensor, a mass flow sensor, and combinations comprising at least one ofthe foregoing sensors. Separated oxidate product stream 76 iscontinuously fed from first vaporization apparatus 52 through one ormore distillation components, e.g., distillation column 58, preferablythree or more distillation components, preferably three distillationcolumns, and exits into second vaporization apparatus 54. Thedistillation column 58 is preferably serially disposed in fluidcommunication between the first vaporizing apparatus 52 and secondvaporizing apparatus 54. The second vaporization apparatus 54reintroduces at least a portion of product stream 46 into thedistillation components 58 to further concentrate and improve the yieldof the resulting concentrated product stream 60. Concentrated productstream 60 is drawn from the distillation column 58, preferably from atleast a portion of the base of distillation column 58. Optionally, arecycled cumene stream 12 (not shown) may be removed from at least aportion of the top of the distillation column 58 to be combined with acumene stream 10 and recycled for reuse in reactors 30, 32, 34, 36, 38and 40.

While the above description represents a preferred embodiment, othersystems and configurations may also be used. For example, one or more ofcumene, water, and ammonia may be fed directly into reactor 30. Additionof aqueous ammonia to one or more returning oxidate or aqueous ammoniarecycle streams may also be used. It is also contemplated that anhydrousammonia, i.e., ammonia gas (NH₃) may be contained in an incoming airfeed stream entering each reactor, separately from or together with theoxygen feed stream. This invention applies equally to both wet and drymodes of cumene oxidation and can also be applied to advantage inanalogous free radical air oxidation processes of other alkylaromaticcompounds, for example air oxidation of ethylbenzene, sec-butylbenzeneand di-isopropylbenzene. The produced cumene hydroperoxide may be usedin a number of applications, including the acid-catalyzed cleavage ofcumene hydroperoxide to phenol and acetone.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLES Comparative Example 1

A 45 day controlled experimental trial was conducted in a continuouscommercial cumene-to-phenol wet oxidation facility as shown in FIG. 2,using a combination of Na₂CO₃ and ammonia as the neutralizing agent.Process data and analytical measurements were collected daily in orderto monitor the progress of the trial over time. Fresh cumene 10 was fedat a rate of 121,000 pounds per hour (lbs/hour) into a settler vesselwhere it was mixed with recycle streams of cumene 12. The resultingtotal organic flow 28 was fed into a six-reactor train 30, 32, 34, 36,38, 40 at a rate of 563,000 lbs/hr. Raw material air 42 was continuouslyfed into the base of each of the six reactors at the followingrespective rates: 36,000, 30,000, 32,000, 29,000, 26,000, and 21,000lbs/hr. The reaction pressure was held at 80 pounds per square inch(psig) in all of the reactors. The temperature maintained in the sixseries reactors was respectively: 225° F., 215° F., 210° F., 205° F.,200° F., and 195° F. The steady-state weight percent CHP concentrationswere maintained inside the six reactors at near 6.0, 11.0, 15.5, 20.0,24.0, 27.0 wt. % concentrations respectively.

Fresh Na₂CO₃ (10 wt. % in aqueous solution) 64 was continuously added tothe top of each of the oxidation reactors in the following respectiveamounts: 260, 209, 203, 200, 189, 181 lbs/hr. The precision of theindividual aqueous Na₂CO₃ flows was measured in advance of the trial runand determined to be +/−1.5 lb/hr. The resultant aqueous phase was drawnoff the bottom of each of the reactors and the combined stream 22 sentto the settler vessel 14. A portion of the aqueous stream collected inthe settler vessel was recycled into the tops of each of the reactors inthe following respective amounts: 17,500, 12,500, 7,500, 4,000, 4,000,4,000 lbs/hr.

44 lbs/hr of anhydrous ammonia was diluted with water to provide 0.5 wt.% NH₄OH/and continuously added to settler vessel. The precision of theammonia flow was measured and determined to be +/−0.5 lb/hr. Inside thesettler vessel the ammonia mixed with the two oxidate phases,partitioned primarily into the bottom aqueous phase in the settlervessel, and was subsequently fed forward in the recycled aqueous phaseto the top of each of the reactors where both the ammonia and mixedalkali-salts entered the individual reactors. Oxidate samples werecollected from each of the reactors for measurement of pH and formicacid and acetic acid content in parts per million (ppm). The organicacids and their respective salts were analyzed using an ion-exclusionchromatography technique.

The 27 wt. % CHP stream 46 emitted from the final reactor represents thefinal cumene-CHP oxidate product. It was continuously transferred to atank 48 for surge and, after settling, was analyzed and its CHP molarselectivity was measured and calculated as a percentage. The cumene-CHPoxidate product 76 was then pumped continuously downstream at a rate of584,000 lbs/hr for further processing at a coalescer vessel 66 andseries of three distillation columns 58.

The 27 wt. % CHP oxidate was also analyzed by atomic absorptiontechnique for sodium contamination. The coalescer oxidate effluent 68was continuously fed forward from the coalescer 66 at a rate of 584,000lbs/hr to the three distillation columns 58 at a rate of 584,000 lbs/hr.Steam heat was provided to the heat exchangers, which were carefullycleaned prior to the beginning of the trial run. At the distillationcolumns most of the cumene present was vaporized, removed overhead byvacuum distillation, and recycled to the settler vessel.

The steam supply to the primary reboiler 54 was controlled by a controlvalve 56 to maintain the desired temperatures in the distillationcolumns 58 and provide a final bottom concentrate of 82 wt. % CHP 60. Asthe reboiler heat exchanger 54 became fouled with salt over time itbecame necessary to open the steam supply valve 56 progressively more toovercome the negative effect of the reduced heat transfer due to thesalt buildup on the heat exchanger tubes. The position of the steamsupply valve (% open) was monitored and used as a good quantitativeindicator of the progressive build up of the salt on the heat exchangertubes as the salt build up fouled the heat exchanger. The final 82 wt. %CHP product 60 was then pumped at a rate of 182,000 lbs/hr to adownstream CHP acid cleavage reaction step where phenol and acetone areproduced from the CHP.

The process performance data obtained from the above 45-day continuousexperiment using the dual base addition process (ammonia plus sodiumcarbonate) is summarized below in Table 1.

TABLE 1 Reactors Product Stream Day Daily pH Formic Acid, CHP, CHP No.Variation ppm wt. % Selectivity, % Phenol, ppm 1 6-8 1100 27 92.4 65 55-9 920 27.5 92.8 45 10 6-8 810 27.5 92.6 45 20 5-8 990 26.8 93 50 305-7 1060 27.5 92.2 60 40 6-8 950 26.7 92.6 60 50 6-9 860 27.2 92.5 65

The above data show wide pH swings occurring frequently within thereactors. This is likely due to free ammonia not being available fordissolution, due to mixed salt formation. This resulted in incompleteremoval of formic acid and negatively impacted the CHP overallselectivity.

During the 45-day trial run, process data was simultaneously collectedon the downstream section of the plant. The obtained data on entrainedsodium in various streams and its accumulated impact on the reboiler andassociated steam supply valve is shown below in Table 2.

TABLE 2 Sodium, ppm Day No. Stream No. 76, 68, 60 Reboiler Valve 56, %open  1 40/2/3 27 10 85/3/3 30 20 62/4/3 40 30 55/5/4 55 40 60/5/5 74 4555/6/5 77

The above results demonstrate that the coalescer was unable to removeall of the entrained sodium salt and that the reboiler becameprogressively fouled as the accumulation of sodium salt depositsincreased during the 45 day trial period.

Example 2

A second trial was conducted for a 26 day period using the same wetcumene oxidation process and conditions used in Example 1, except thatammonia was employed as the sole alkaline treating agent. As before, 44lbs/hr of 0.5 wt. % ammonium hydroxide was added to the settler vessel.The reboiler was thoroughly cleaned prior to beginning the test run.

Process performance and analytical data was collected daily and aresummarized below in Table 3:

TABLE 3 Reactors Product Stream Day Daily pH Formic CHP, CHP No.Variation Acid, ppm wt. % Selectivity, % Phenol, ppm 1 7-8 220 28 93.525 5 7-9 180 27.5 92.8 28 15 7-8 310 27 93.4 35 26 7-9 290 27.8 93.6 35

The results show that the pH of the reaction is more closely controlled,organic acids more effectively neutralized, and phenol formation isreduced which is beneficial for CHP yields (selectivity).

Since no alkali-salt agents were added to the system during this 26-daytrial run, no sodium contamination was expected in the downstreamprocess streams and no negative impact on reboiler performance due tofouling was expected. Table 4 summarizes the data collected daily forconfirmation of these expectations.

TABLE 4 Sodium, ppm Reboiler Valve 56, Day No. Stream No. 76, 68, 60 %open  1 1/1/1 25 10 1/0/0 25 26 0/0/0 25

As shown by the above data, the position of the steam supply valve forthe reboiler was unchanged during the 26-day trial run period,indicating no salt deposits or fouling of any kind.

Example 3

A third plant trial run was conducted for a 40 day period using the sameconditions as in Example 2, except that only 24 lbs/hr of 0.5 wt. %ammonia solution was added to the settler vessel. No other alkalineagents were employed. Table 5 summarizes the data collected daily duringthe 40-day period.

TABLE 5 Reactors Product Stream Day Daily pH Formic No. Variation Acid,ppm CHP, wt. % CHP Selectivity, %  1 5-6 390 28 93 20 6-7 330 27.7 92.640 5-6 405 27.6 93.1

Also during this 40 day trial the downstream measurement of sodium wascontinued daily. Table 6 summarizes the data collected daily during the40-day period.

TABLE 6 Sodium, ppm Reboiler Day No. Stream No. 76, 68, 60 Valve 56, %open  1 0/0/0 28 20 0/0/0 28 40 0/0/0 28

This data reinforces the results of Example 2 indicating that very lowamounts of ammonia can be effectively and beneficially used as the soleneutralizing agent in a wet cumene oxidation process.

The method and system for manufacturing cumene hydroperoxide using freeammonia in a wet oxidation process with concurrent elimination of alkaliand alkaline salt or base additives possesses several advantages overconventional processes, including the option to use wet oxidation,elimination of multiple neutralization agents, improved pH control,reduced phenol inhibitor formation, lower initial plant investment,higher plant on-stream factor, increased production rate, andelimination of complex systems and expensive equipment.

In particular, the free ammonia method may be conducted using thepreferred safety “wet oxidation mode”. The heterogeneous wet oxidationmethod is preferred over the alternative dry cumene oxidation method asthe presence of a separate water phase inside the oxidation reactorsprovides enhanced cooling of the reaction via its evaporation, thusgiving improved heat removal of the exothermic heat of reaction, and amore precise reactor temperature control. Also, the wet oxidationprocess requires less investment due to the use of less costly materialsof construction.

The free ammonia method also does not employ troublesome alkali-metalsalt additives. There are accordingly none of the immiscible, insolubleorganic and alkaline phases, slowed mass transfer and lower degree ofmixing between such phases, fouling of equipment due to salt deposits,or fluctuation of pH, each of which may require complex systems toovercome. The inventive method thus eliminates the need for complexsystems and expensive equipment, and requires a lower initial plantinvestment, as there is no requirement for special equipment such asstatic mixers, counter-current extractors or coalescer units. Theinventive process also employs a smaller quantity of ammonia as aneutralizing agent, which eliminates the need for periodic cleaning andplant shut downs associated with alkali and alkaline earth metaladditives. Ammonia also acts as a single agent and is continuouslyavailable to neutralize acid inhibitors, and prevent phenol formationthroughout the wet cumene oxidation process. Even though ammonia is notdibasic in nature and possesses no “inherent” buffering properties, thepH can be controlled more effectively, i.e., a tighter pH range isestablished, using ammonia than alkali-metal salt additives.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A system for producing cumene hydroperoxide,comprising: a cumene feed in fluid communication with a reactor having acumene hydroperoxide oxidate outlet; an oxygen feed in fluidcommunication with the reactor; and an ammonium hydroxide feed in fluidcommunication with the cumene feed and/or the reactor, wherein thecumene feed, the oxygen feed, the ammonium hydroxide feed, and thereactor are free of an additive comprising an alkali or alkaline earthmetal.
 2. The system of claim 1 further comprising a storage dischargeserially disposed in fluid communication with the reactor outlet.